Complex forest scene SAR data simulation method, device, equipment and medium

Abstract

The present disclosure provides a method for simulating SAR data of a complex forest scene, including: constructing a ground surface geometry model, a tree geometry model and an electric tower geometry model to generate a three-dimensional geometry model of the complex forest scene; gridding the three-dimensional geometry model of the complex forest scene to obtain a transmission matrix and an occlusion matrix in each grid; based on the occlusion matrix, identifying the unoccluded parts of trees, ground surface and electric towers in each grid, and calculating the tree scattering matrix, the ground surface scattering matrix and the electric tower scattering matrix of each grid based on the transmission matrix, and calculating the electric tower scattering matrix includes: decomposing the electric tower into a plate and a dihedral angle, and after calculating the scattering matrices respectively, jointly forming the electric tower scattering matrix; using the tree scattering matrix, the ground surface scattering matrix and the electric tower scattering matrix as input to simulate SAR echo data, and performing imaging processing to obtain SAR image data of the complex forest scene. The present disclosure also provides a device, equipment and medium for simulating SAR data of a complex forest scene.

Description

Technical Field

[0001] The present disclosure relates to the field of radar signal processing technology, and in particular to a complex forest scene SAR data simulation method, device, electronic equipment and medium. Background Art

[0002] A forest is a complex ecosystem that includes not only natural objects such as trees, grasslands, and ground surfaces, but also artificial objects such as roads, farmlands, and electric towers. However, current forest scene simulation models mainly model elements such as trees, grasslands, and ground surfaces, and few simulation models that include artificial objects have been proposed. In practical applications, in order to ensure the normal operation of the power system, high-voltage lines need to be inspected regularly. Some high-voltage electric towers are built in mountainous areas where few people go. These areas have steep terrain slopes and high forest density. The use of manual inspections is not only inefficient but also very dangerous. Therefore, it is of great research significance to construct a complex forest scene model with electric towers to replace manual inspections. Summary of the invention

[0003] In view of the above problems, the present invention provides a complex forest scene SAR data simulation method to solve the above technical problems.

[0004] A first aspect of the present disclosure provides a method for simulating SAR data of a complex forest scene, comprising: constructing a ground surface geometric model, a tree geometric model and an electric tower geometric model, randomly distributing the tree geometric model and the electric tower geometric model on the ground surface constructed by the ground surface geometric model, and generating a three-dimensional geometric model of the complex forest scene; simulating a radar to transmit electromagnetic waves in the complex forest scene; gridding the three-dimensional geometric model of the complex forest scene, and obtaining an occlusion matrix and a transmission matrix of each grid based on the occlusion and attenuation of electromagnetic waves in each grid; identifying the unoccluded parts of trees, ground surface and electric towers in each grid based on the occlusion matrix, and calculating the tree scattering matrix, the ground surface scattering matrix and the electric tower scattering matrix of the unoccluded parts of trees, ground surface and electric towers in each grid based on the transmission matrix, wherein calculating the electric tower scattering matrix comprises: decomposing the electric tower into a plate and a dihedral angle, and respectively calculating the scattering matrices of the plate and the dihedral angle to form a tower scattering matrix together; using the tree scattering matrix, the ground surface scattering matrix and the electric tower scattering matrix as input to simulate SAR echo data, and performing imaging processing to obtain SAR image data of the complex forest scene.

[0005] According to an embodiment of the present disclosure, the three-dimensional geometric model of the complex forest scene is gridded, and the occlusion matrix and transmission matrix of each grid are obtained based on the occlusion and attenuation of the electromagnetic waves in each grid, including: calculating the horizontal polarization attenuation coefficient and the vertical polarization attenuation coefficient of the radar electromagnetic wave penetrating each of the grids, setting the cross polarization to 0, and obtaining the transmission matrix of the grid; calculating the surface peak point passed through on the straight-line distance between the radar and the preset target position of each of the grids to obtain the angle between the surface peak point and the target position in the vertical direction; when the angle is less than the lower viewing angle between the radar and the target position, it is judged that the target position is not blocked by the surface, otherwise it is judged that the target position is blocked by the surface; according to whether each target position of the grid in the complex forest scene is blocked, an occlusion matrix is ​​constructed, wherein each element in the occlusion matrix corresponds to each target position in the grid, and its element value is 1 or 0, indicating that the target position is not blocked or blocked, respectively, and the target position includes the location of trees, the surface, and the electric tower.

[0006] According to an embodiment of the present disclosure, the tree scattering matrix, the ground scattering matrix and the tower scattering matrix of the unobstructed parts of the trees, the ground and the towers in each of the grids based on the transmission matrix include: based on the geometric information of the unobstructed trees in the grid, using the electromagnetic scattering radiation transmission equation to calculate the initial scattering matrix of the trees; obtaining the transmission matrix of each grid that the tree passes through at a straight-line distance from the radar, multiplying the initial scattering matrix by the transmission matrix of each grid to obtain the tree scattering matrix; dividing the unobstructed ground in the grid into a plurality of small planes, using the OH model to calculate the initial scattering matrix of each small plane; obtaining the transmission matrix of each small plane The transmission matrix of each grid passed by the surface on the straight-line distance between the surface and the radar is obtained, and the initial scattering matrix of each small plane is multiplied by the transmission matrix of each corresponding grid to obtain the scattering matrix of each small plane, and together constitute the surface scattering matrix; the unobstructed tower in the grid is decomposed into multiple flat plates and multiple dihedral angles, and the initial scattering matrix of each flat plate and dihedral angle is calculated; the transmission matrix of each grid passed by each flat plate and dihedral angle on the straight-line distance between the surface and the radar is obtained, and the initial scattering matrix of each flat plate and dihedral angle is multiplied by the transmission matrix of each corresponding grid to obtain the scattering matrix of each flat plate and dihedral angle, and together constitute the tower scattering matrix.

[0007] According to an embodiment of the present disclosure, calculating the initial scattering matrix of the dihedral angle includes: calculating the initial scattering matrix of the dihedral angle based on six positional relationships between the dihedral angle and the incident direction of the radar electromagnetic wave; wherein, the intersection line of the two plates constituting the dihedral angle is used as the z-axis, the angle bisector is used as the x-axis, and the y-direction is determined according to the right-hand rule, represents half of the included angle of the dihedral angle, represents the angle between the incident direction of the electromagnetic wave and the angle bisector of the dihedral angle, S1, S2, S3, S4, S5 and S6 represent the initial scattering matrices corresponding to the six position relationships, respectively. and The primary scattering matrices of the two plates represent the dihedral angles, and The primary scattering matrices of the two back surfaces of the two plates represent the dihedral angles, The secondary scattering matrix representing the dihedral angle of plane a reflected to plane b, It represents the secondary scattering matrix of plane b reflected to plane a. The side with an angle greater than 180° between the two planes is the back side.

[0008] when hour, ;

[0009] when hour, ;

[0010] when hour, ;

[0011] when hour, ;

[0012] when hour, ;

[0013] when hour, .

[0014] According to an embodiment of the present disclosure, calculating a primary scattering matrix or a secondary scattering matrix of a dihedral angle includes:

[0015] ;

[0016] ;

[0017] ;

[0018] ;

[0019] in, , , and represent the four diagonal elements of the primary scattering matrix or the secondary scattering matrix respectively, Indicates that the incident direction of the electromagnetic wave emitted by the radar is The angle between the projection of the plane and the x-axis, represents the incident direction of the electromagnetic wave and The plane angle, k represents the beam, r represents the distance from the radar to the target, λ represents the wavelength, a and b represent the width of the two plates of the dihedral angle that the electromagnetic wave can illuminate, and c represents the length of the two plates. and is the irradiation length of the electromagnetic wave reflected from one plane of the dihedral angle to the other plane;

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] According to an embodiment of the present disclosure, when calculating a primary scattering matrix, the equivalent scattering center of the primary scattering is considered to be at the center of each plate; when calculating a secondary scattering matrix, the position of the equivalent scattering center needs to be calculated according to the angle of the incident light.

[0026] According to an embodiment of the present disclosure, calculating the initial scattering matrix of the plate includes:

[0027]

[0028] Where S represents the scattering coefficient of the plate, represents the incident direction of the electromagnetic wave used to detect the grid, represents the polarization of the incident electromagnetic wave, Indicates the reflection direction, represents the polarization mode of the reflected electromagnetic wave, k represents the beam, a and b represent the length and width of the plate, represents the incident angle of the electromagnetic wave, represents the reflection angle of the electromagnetic wave, is the plane normal.

[0029] The second aspect of the present disclosure provides a SAR data simulation device for a complex forest scene, including: a scene modeling module, which is used to construct a surface geometry model, a tree geometry model and an electric tower geometry model, and randomly distribute the tree geometry model and the electric tower geometry model on the surface constructed by the surface geometry model to generate a three-dimensional geometry model of the complex forest scene; a radar simulation module, which is used to simulate the radar transmitting electromagnetic waves in the complex forest scene; a grid division module, which is used to grid the three-dimensional geometry model of the complex forest scene, and obtain the transmission matrix and the occlusion matrix of each grid based on the occlusion and attenuation of the electromagnetic waves in each grid; a scattering matrix calculation module, which is used to calculate the transmission matrix and the occlusion matrix of each grid; Based on the occlusion matrix, the unoccluded parts of trees, ground and electric towers in each grid are identified, and based on the transmission matrix, the tree scattering matrix, the ground scattering matrix and the electric tower scattering matrix of the unoccluded parts of trees, ground and electric towers in each grid are calculated, wherein the calculation of the electric tower scattering matrix includes: decomposing the electric tower into a plate and a dihedral angle, and respectively calculating the scattering matrices of the plate and the dihedral angle to form a tower scattering matrix together; an image simulation module is used to use the tree scattering matrix, the ground scattering matrix and the electric tower scattering matrix as input simulated SAR echo data, and perform imaging processing to obtain SAR image data of complex forest scenes.

[0030] The third aspect of the present disclosure provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, each step of the complex forest scene SAR data simulation method described in any one of the first aspects is implemented.

[0031] A fourth aspect of the present disclosure provides a computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, each step in any one of the complex forest scene SAR data simulation methods in the first aspect is implemented.

[0032] At least one of the above technical solutions adopted in the embodiments of the present disclosure can achieve the following beneficial effects:

[0033] The present invention provides a SAR data simulation method for complex forest scenes and proposes a forest-electricity tower hybrid scene simulation model. The simulation method has high realism and can provide technical support for the research on electric tower target detection technology in forest areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0035] Figure 1 A flowchart of a complex forest scene SAR data simulation method provided by an embodiment of the present disclosure is schematically shown;

[0036] Figure 2 A schematic diagram of a complex forest scene SAR data simulation method provided by an embodiment of the present disclosure is schematically shown;

[0037] Figure 3 A schematic diagram of the principle of a ground surface fractal model provided by an embodiment of the present disclosure is schematically shown;

[0038] Figure 4 A schematic diagram of a tree fractal model process provided by an embodiment of the present disclosure is shown schematically;

[0039] Figure 5 Schematic diagrams of various electric towers provided by embodiments of the present disclosure are shown;

[0040] Figure 6 A schematic diagram of transmission matrix calculation provided by an embodiment of the present disclosure is schematically shown;

[0041] Figure 7 The schematic diagram of scattering matrix calculation provided by the embodiment of the present disclosure is schematically shown;

[0042] Figure 8 The schematic diagram of ground obstruction judgment provided by the embodiment of the present disclosure is schematically shown;

[0043] Fig. 9 The schematic diagram of the metal flat plate provided by the embodiment of the present disclosure is schematically shown;

[0044] Fig.10 Schematically shows a schematic diagram of a dihedral angle geometric structure provided by an embodiment of the present disclosure;

[0045] Fig.11 Schematically showing six positional relationships between dihedral angles and incident directions provided by an embodiment of the present disclosure;

[0046] Fig.12 A schematic diagram schematically shows a first positional relationship between a dihedral angle and an incident direction provided by an embodiment of the present disclosure;

[0047] Fig.13A A schematic diagram of an equivalent scattering center of a dihedral angle provided by an embodiment of the present disclosure is schematically shown;

[0048] Fig. 13B A schematic diagram of an equivalent scattering center of a dihedral angle provided by an embodiment of the present disclosure is schematically shown;

[0049] Fig.14 A schematic diagram schematically shows a second positional relationship between a dihedral angle and an incident direction provided by an embodiment of the present disclosure;

[0050] Fig.15A schematic diagram schematically shows a third positional relationship between a dihedral angle and an incident direction provided by an embodiment of the present disclosure;

[0051] Fig.16 A schematic diagram schematically shows a fourth positional relationship between a dihedral angle and an incident direction provided by an embodiment of the present disclosure;

[0052] Fig.17 A schematic diagram schematically shows a fifth positional relationship between a dihedral angle and an incident direction provided by an embodiment of the present disclosure;

[0053] Fig.18 A schematic diagram schematically shows a sixth positional relationship between a dihedral angle and an incident direction provided by an embodiment of the present disclosure;

[0054] Fig.19A The simulated SAR image of an electric tower provided by an embodiment of the present disclosure is schematically shown;

[0055] Fig.19B The SAR image of a power tower measured in an embodiment of the present disclosure is schematically shown;

[0056] Fig. 20 The SAR data simulation results of the forest-power tower hybrid scene provided by the embodiment of the present disclosure are schematically shown;

[0057] Fig.21 A structural block diagram of a complex forest scene SAR data simulation device provided by an embodiment of the present disclosure is schematically shown;

[0058] Fig. 22 The structural block diagram of an electronic device provided by an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0059] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0060] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0061] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0062] Some block diagrams and / or flow charts are shown in the accompanying drawings. It should be understood that some blocks or combinations thereof in the block diagrams and / or flow charts may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that these instructions, when executed by the processor, may create a device for implementing the functions / operations described in these block diagrams and / or flow charts.

[0063] Therefore, the technology of the present disclosure can be implemented in the form of hardware and / or software (including firmware, microcode, etc.). In addition, the technology of the present disclosure can take the form of a computer program product on a computer-readable medium storing instructions, which can be used by an instruction execution system or in combination with an instruction execution system. In the context of the present disclosure, a computer-readable medium can be any medium that can contain, store, transmit, propagate, or transmit instructions. For example, a computer-readable medium can include, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, device, or propagation medium. Specific examples of computer-readable media include: magnetic storage devices, such as magnetic tape or hard disk (HDD); optical storage devices, such as compact disk (CD-ROM); memory, such as random access memory (RAM) or flash memory; and / or wired / wireless communication links.

[0064] The disclosed embodiment provides a method for simulating SAR data of a complex forest scene. For forest targets, the traditional Monte Carlo coherent scattering model based on the fractal model is used for simulation; for power tower targets, the power tower is simplified into a composite target composed of a flat plate and a metal dihedral, and the scattering coefficient of each component is calculated using a physical optics method. Finally, the influence of target attenuation and occlusion during electromagnetic wave propagation is considered to generate scattering data of the entire scene.

[0065] Figure 1 The flowchart of a complex forest scene SAR data simulation method provided by an embodiment of the present disclosure is schematically shown. Figure 2 A schematic diagram of a complex forest scene SAR data simulation method provided by an embodiment of the present disclosure is schematically shown.

[0066] like Figure 1 and Figure 2 As shown, a complex forest scene SAR data simulation method provided by an embodiment of the present disclosure includes operations S110 to S150.

[0067] S110, constructing a ground surface geometric model, a tree geometric model and an electric tower geometric model, randomly distributing the tree geometric model and the electric tower geometric model on the ground surface constructed by the ground surface geometric model, and generating a three-dimensional geometric model of a complex forest scene.

[0068] In this embodiment, a surface geometric model can be established by a fractal model. The fractal model is established on the basis of fractal geometry, and generates geometric structures with different characteristics according to set initial parameters by establishing a certain recursive relationship. The fractal model can use fewer parameters to perform geometric modeling on a single tree, generate a single tree structure with higher fidelity, and use an iterative method that is conducive to computer implementation, which is currently a more widely used method.

[0069] High-voltage electric towers are generally steel frame structures, consisting of three parts: tower head, tower body, and tower legs. The electrical equipment on them includes lightning rods, conductors, insulators, grounding wires, grounding devices, spacers, etc. Accurately simulating the scattering intensity of each part of the electric tower is very complicated. In order to simplify the model, in this embodiment, only the steel frame structure of the electric tower is modeled. The steel frame structure is decomposed into two structures: metal flat plate and metal dihedral angle, and a simulation model is established using professional 3D mapping software.

[0070] In this embodiment, the constructed tree geometry model and power tower geometry model can be randomly or according to the actual geographical location distribution and the surface geometry model to form a complex deep forest simulation scene.

[0071] S120, simulating a radar to transmit electromagnetic waves in the complex forest scene.

[0072] S130, gridding the three-dimensional geometric model of the complex forest scene, and obtaining an occlusion matrix and a transmission matrix in each grid based on the occlusion and attenuation of electromagnetic waves in each grid.

[0073] In this embodiment, the forest-power tower hybrid scene contains multiple targets. In order to simulate the impact between different targets, it is necessary to consider the attenuation effect of the electromagnetic wave propagation process and the occlusion relationship between different targets. The entire scene is divided into three-dimensional grids, and the impact of the tree canopy on the attenuation of electromagnetic waves and the impact of the undulating surface on the occlusion of electromagnetic waves in each grid are calculated to generate the transmission matrix and occlusion matrix of the entire scene.

[0074] In this embodiment, it is considered that the attenuation effect and shielding effect of the electric tower on the electromagnetic wave are small, so it is not considered when calculating the shielding matrix and the transmission matrix. The transmission matrix of the entire scene is obtained by calculating the total length of the electromagnetic wave passing through the tree canopy in each grid and calculating the transmission coefficient of each grid. Since the undulation of the ground surface will shield the electromagnetic wave, for the shielded target, it is considered that there is no backscattering. According to the location of the radar and the location of the detection target, it is judged whether the detection target is shielded to construct the shielding matrix.

[0075] S140, based on the occlusion matrix, identifying the unobstructed parts of trees, ground and towers in each grid, and calculating the tree scattering matrix, ground scattering matrix and tower scattering matrix of the unobstructed parts of trees, ground and towers in each grid based on the transmission matrix, wherein calculating the tower scattering matrix includes: decomposing the tower into a plate and a dihedral, and calculating the scattering matrices for each of them, and together forming the tower scattering matrix.

[0076] Calculate the scattering coefficients of targets such as the ground, trees, and high-voltage towers in the scene, and consider the effects of target attenuation and occlusion during electromagnetic wave propagation. The ground is calculated using the OH model, the trees are calculated using the classical scattering particle model, and the high-voltage towers are calculated using the physical optics method. If the occlusion matrix of the grid through which the straight line to the radar position passes has a value of 0, the grid unit detected by the radar is considered to be blocked and the scattering coefficient is not calculated.

[0077] S150, simulating SAR echo data based on the tree scattering matrix, the ground scattering matrix and the power tower scattering matrix, and performing imaging processing to obtain a SAR simulation image of the complex forest scene.

[0078] Optionally, based on the generated scene scattering data, a range frequency-domain pulse coherent (RFTC) algorithm may be used to generate SAR echo data, and a BP (backprojection) imaging algorithm may be used to generate SAR image data.

[0079] Figure 3 A schematic diagram of the principle of a surface fractal model provided by an embodiment of the present disclosure is schematically shown.

[0080] like Figure 3 As shown, the embodiment of the present disclosure provides a schematic diagram of the principle of a surface fractal model. The fractal model uses a random midpoint iteration method to generate the height information of the center position according to the four corner points of the square, and continuously iterates and refines the grid accuracy until the set number of iterations is reached. The formula for calculating the center point height is:

[0081] in, is the height attribute value of the nth iteration, is with The height attribute values ​​of the four adjacent corner points, is the maximum surface elevation, is the surface roughness, which is a constant between [0,1). The smaller the value, the smoother the surface. is a uniformly distributed random number in the range [-0.5, 0.5].

[0082] Figure 4 A schematic diagram of a tree fractal model process provided by an embodiment of the present disclosure is shown schematically.

[0083] like Figure 4 As shown, the modeling process of the tree fractal model includes: first determine the length and position of the trunk; then establish the primary branches and secondary branches according to the fractal method, and continuously iterate and refine; finally, randomly generate a certain number of leaves around the branches.

[0084] In the fractal process, the length and radius of the branches decrease with the recursive process. Each branch is divided into two or more branches at the splitting node. The radius of the new branch and the original branch needs to satisfy a certain relationship. A commonly used method to calculate the branch radius is to use the area invariance principle, that is, the cross-sectional area of ​​the original branch is equal to the sum of the cross-sectional areas of the split branches.

[0085] ;

[0086] in, is the radius of the original branch root node, It is The radius of the root node of the split branch, is the radius ratio of the original branch and the split branch, when When , the original branches and the split branches meet the area invariance principle. Another fractal parameter that needs to be concerned is the length ratio of the original branches and the split branches. :

[0087] ;

[0088] in, is the length of the branch, is the length of the original branch. For the single tree structure of a three-dimensional forest, the angle between the original branch and the split branch also needs to be considered, including the inclination angle and the rotation angle. These parameters can be obtained based on the measured data.

[0089] The leaves of different tree species vary greatly. To simplify the simulation model, conifer leaves are approximated by thin cylinders, and broadleaf leaves are approximated by disks. In nature, leaves grow around branches and are distributed in "clusters". To simplify the modeling, the leaves are regarded as tiny particles inside the crown, which are randomly distributed inside the crown.

[0090] The size and shape of the tree crown vary depending on the tree species. Most tree crowns can be approximated as ellipsoids or cones. Since the lateral branches of deciduous trees grow faster, the central trunk will be shaded by the lateral branches and eventually form a crown that is approximately ellipsoidal; the lateral branches of coniferous trees grow slower, and eventually the crown will form a cone structure. In this implementation, the geometric models of different types of trees can be reasonably constructed according to the distribution of tree species in the actual forest scene.

[0091] Figure 5 Schematic diagrams of various electric towers provided by embodiments of the present disclosure are schematically shown.

[0092] like Figure 5 As shown, the structure of the high-voltage electric tower is complex and diverse. According to the different structural forms, it can be divided into a wine glass type 501, a cat head type 502, a dry type 503, a drum type 504, etc. The high-voltage electric tower is generally a steel frame structure, which consists of three parts: a tower head, a tower body, and a tower leg. The electrical equipment on it includes a lightning rod, a conductor, an insulator, a grounding wire, a grounding device, a spacer, etc. The accurate simulation of the scattering intensity of each part of the electric tower is very complex. In order to simplify the model, this embodiment only models the steel frame structure of the electric tower. The steel frame structure is decomposed into two structures: a metal plate and a metal dihedral angle, and a simulation model is established using professional 3D mapping software.

[0093] Figure 6 The schematic diagram of transmission matrix calculation provided by the embodiment of the present disclosure is schematically shown.

[0094] like Figure 6 As shown, the simulation scene is divided into three-dimensional grids, the total length of the electromagnetic wave passing through the tree crown in each grid is calculated, the transmission coefficient of each grid is calculated, and the transmission matrix of the entire scene is obtained.

[0095] Specifically, calculating the transmission matrix includes S610 to S620.

[0096] S610, calculating the attenuation coefficient of the radar electromagnetic wave, where the attenuation coefficient at least includes the path length of the electromagnetic wave passing through the trees in the grid.

[0097] S620, calculating a horizontal polarization attenuation coefficient and a vertical polarization attenuation coefficient based on the attenuation coefficient, setting the cross polarization to 0, and obtaining a transmission matrix of the grid.

[0098] in, is the total tree crown length in the i-th row, j-th column, and k-th grid at the radar location for:

[0099] ;

[0100] Where N is the number of tree crowns in the grid, is the length of the electromagnetic wave penetrating the t-th tree crown. According to the length of the electromagnetic wave penetrating the tree crown, the transmission matrix at different positions is calculated using the Foldy approximation. .

[0101] .

[0102] Figure 7 The schematic diagram of scattering matrix calculation provided by an embodiment of the present disclosure is schematically shown.

[0103] like Figure 7 As shown, for a single scattering, the paths traversed by the incident electromagnetic wave and the reflected electromagnetic wave are the same. Therefore, the transmission matrix in the incident direction is the same as the transmission matrix in the reflected direction. The final scattering matrix can be expressed as:

[0104] ;

[0105] in, is the scattering matrix without considering the attenuation of electromagnetic waves, is the incident direction transmission matrix. is the primary scattering matrix. For secondary scattering, the scattering matrix can be expressed as:

[0106] ;

[0107] in, , , is the transmission matrix of different paths such as Figure 7 As shown, is the surface Fresnel reflection matrix, is the secondary scattering matrix.

[0108] Figure 8 A schematic diagram of ground surface obstruction judgment provided by an embodiment of the present disclosure is schematically shown.

[0109] like Figure 8 As shown, R is the radar location, T is the target location, the target location includes trees, ground surface, and power towers. The radar beam is below the viewing angle. Illuminating the ground, P is the peak value of the surface between the radar and the target, It is the vertical angle between the target position and the peak point.

[0110] Determining whether there is ground obstruction includes S810 to S820.

[0111] S810, obtaining the surface peak point P passed by the radar and the preset target position of each grid in the straight line distance, so as to obtain the distance between the surface peak point and the target position. Angle in the vertical direction .

[0112] S820, when the angle , it is determined that the target position is not blocked by the ground surface; otherwise, it is determined that the target position is blocked by the ground surface.

[0113] S830, constructing an occlusion matrix according to whether each target position of the grid in the complex forest scene is occluded, wherein each element in the occlusion matrix corresponds to each target position in the grid, and its element value is 0 or 1, indicating that the target position is occluded or not occluded, respectively.

[0114] Since there may be multiple peak points between the target and the radar, multiple judgments are required. l is the line from the target to the radar. Calculate the elevation value of each point of the projection of the straight line l on the ground And the horizontal distance from this point to the target ,make equal:

[0115] ;

[0116] When any When , the target is considered not to be blocked by the ground surface, otherwise it is considered to be blocked by the ground surface.

[0117] After the transmission matrix and the occlusion matrix are obtained, according to S140, the method for calculating the tree scattering matrix, the ground scattering matrix and the tower scattering matrix is ​​as follows.

[0118] In the disclosed embodiment, when calculating the scattering matrix of trees in a complex forest scene, the position of each branch, leaf, trunk and radar of the tree is determined respectively to determine whether it is blocked. If the occlusion matrix through which the straight line to the radar position passes has a value of 0, the scattering unit is considered to be blocked and the scattering coefficient is not calculated. Calculating the scattering matrix of unblocked trees includes S141~S142.

[0119] S141, based on the geometric information of the unobstructed trees in the grid, using the radiation transfer equation to calculate the initial scattering matrix of the trees.

[0120] S142, obtaining the transmission matrix of each grid that the tree passes through in the straight-line distance between the tree and the radar, and multiplying the initial scattering matrix by the transmission matrix of each grid to obtain the tree scattering matrix.

[0121] Among them, trees can be regarded as a complex composed of trunks, branches, and leaves, where trunks and thick branches are approximated by long cylinders, small branches and needle-shaped leaves are approximated by thin cylinders, and broad-leaved leaves are approximated by disks. Therefore, the forest can be decomposed into classical scattering particles such as long cylinders, thin cylinders, and disks. If it is not blocked, the scattering matrix of each structure of the tree is calculated based on the geometric information of the tree (the size, position, direction, dielectric constant, etc. of branches, leaves, and trunks). Using the classical electromagnetic scattering method, the scattering matrix of each scattering unit (leaves, leaves, etc.) is calculated, and many scattering matrices will be calculated for each tree. Each scattering matrix has a position information, which is the same as the position of the scattering unit (branches, leaves, trunks).

[0122] In the embodiment of the present disclosure, the calculation of the surface scattering matrix first determines whether the surface is blocked, and for the surface without blocking, the following operations are performed.

[0123] S143, dividing the unobstructed ground surface in the grid into a plurality of small planes, and using the OH model to calculate an initial scattering matrix of each small plane.

[0124] Among them, the small facet is much smaller than the resolution. According to the information of surface dielectric constant, surface roughness, incident angle, etc., the classic OH model is used to calculate the scattering matrix of each small facet.

[0125] The surface of the earth in nature can be regarded as a random rough surface with a certain dielectric constant and correlation length. At present, many surface scattering models have been proposed, such as the small perturbation model (SPM), Kirchhoff model (KM), integral equation model (IEM), semi-empirical model (OH), Dubois model, etc. Among them, the OH model is an empirical model proposed by Oh et al. using the collected full polarization data of multiple frequency bands (L, C, X), various soil moisture contents, surface roughness, and downward viewing angles through regression analysis. The formula is:

[0126]

[0127] in, is the normalized backscatter coefficient, is the co-polarization ratio, is the cross-polarization ratio, is the dielectric constant, is the RMS height of the ground surface, is the free space wave number, is the angle of incidence, is the correlation constant, is the volumetric water content of the soil, is the Fresnel reflection coefficient. The OH model has a , , , The predicted values ​​within the range are better.

[0128] S144, obtaining the transmission matrix of each grid that each of the small planes passes through in the straight-line distance from the radar, multiplying the initial scattering matrix of each of the small planes by the transmission matrix of each corresponding grid to obtain the scattering matrix of each of the small planes, and together forming the surface scattering matrix.

[0129] According to the above method, a lot of scattering matrices are calculated for the surface of a grid unit, and the position of each scattering matrix is ​​the same as the position of a small surface.

[0130] In the disclosed embodiment, the tower scattering matrix is ​​calculated to first determine whether the tower is blocked. For the ground surface without blocking, the following operations are performed.

[0131] S145, decomposing the unobstructed towers in the grid into a plurality of flat plates and a plurality of dihedral angles, and calculating an initial scattering matrix of each flat plate and dihedral angle.

[0132] S146, obtaining the transmission matrix of each grid that each of the flat panels and dihedral angles passes through in the straight-line distance from the radar, and multiplying the initial scattering matrix of each of the flat panels and dihedral angles by the transmission matrix of each corresponding grid, to obtain the scattering matrix of each of the flat panels and dihedral angles, and together constitute the scattering matrix of the tower.

[0133] The calculation of the tower scattering matrix is ​​described in detail below.

[0134] Fig. 9 A schematic diagram of a metal flat plate provided by an embodiment of the present disclosure is schematically shown.

[0135] like Fig. 9 As shown, the metal plate provided in the embodiment of the present disclosure has an incident direction of electromagnetic waves of , the polarization mode is , the reflection direction is , the polarization mode is , according to the approximate formula of physical optics:

[0136] ;

[0137] Where k represents the beam, a and b represent the length and width of the plate, represents the incident angle of the electromagnetic wave, represents the reflection angle of electromagnetic waves, is the plane normal.

[0138] Fig.10 The schematic diagram of the dihedral angle geometric structure provided by the embodiment of the present disclosure is schematically shown.

[0139] like Fig.10 As shown, the dihedral angle can be regarded as composed of two metal plates, where a and b are the widths of the two plates, and c is the length of the two plates. The intersection of the two plates is used as the z-axis, the angle bisector is used as the x-axis, and the y-direction is determined according to the right-hand rule. is half of the dihedral angle, The incident light is The angle between the projection of the plane and the x-axis, is the incident light and Plane angle.

[0140] According to the physical optics method, the scattered field H can be expressed as:

[0141] ;

[0142] In the formula, is the surface unit normal vector, is the incident magnetic field strength at a point on the surface, is the radial vector from the origin to the integration point on the surface, k is the wave number, is the radial unit vector from the origin to the field point.

[0143] Assuming a plane wave is incident on the dihedral angle, the incident magnetic field is:

[0144] ;

[0145] In the formula , is the incident wave direction, is the amplitude, for horizontal polarization , for vertical polarization , the incident direction is limited to Then the complex scattering matrix of the dihedral angle can be expressed as

[0146] ;

[0147] ;

[0148] ;

[0149] ;

[0150] in, , , and represent the four diagonal elements of the primary scattering matrix or the secondary scattering matrix respectively, Indicates that the incident direction of the electromagnetic wave emitted by the radar is The angle between the projection of the plane and the x-axis, represents the incident direction of the electromagnetic wave and The plane angle, k represents the beam, r represents the distance from the radar to the target, λ represents the wavelength, a and b represent the width of the two plates of the dihedral angle that the electromagnetic wave can illuminate, and c represents the length of the two plates. and is the irradiation length of the electromagnetic wave reflected from one plane of the dihedral angle to the other plane;

[0151]

[0152]

[0153]

[0154]

[0155]

[0156] Fig.11 Schematic diagrams showing six positional relationships between dihedral angles and incident directions provided in an embodiment of the present disclosure.

[0157] like Fig.11 As shown in the figure, the dihedral angle can be calculated in 6 cases according to the different directions of the incident light. Starting from the bisector of the dihedral angle and moving clockwise as positive, the angle between the incident light and the bisector of the angle in the six cases is , as shown in Table 1. The dihedral angles calculated in the embodiment of the present disclosure are all right angles, where Equal to 45°.

[0158] Table 1 Relationship between dihedral angle and incident light in 6 cases

[0159]

[0160] Fig.12 A schematic diagram of the first positional relationship between the dihedral angle and the incident direction provided by an embodiment of the present disclosure is schematically shown.

[0161] like Fig.12 As shown, when the angle between the incident light and the bisector of the dihedral angle is exist When , it is necessary to calculate the primary scattering of the two planes of the dihedral angle and the secondary scattering between the two planes. The total scattering matrix of the dihedral angle can be expressed as :

[0162] ;

[0163] in, and are the primary scattering matrices of planes a and b, respectively, is the secondary scattering matrix reflected from plane a to plane b, is the secondary scattering matrix reflected from plane b to plane a.

[0164] The equivalent scattering center of primary scattering is considered to be at the center of each plate. For secondary scattering, the position of the equivalent scattering center needs to be calculated according to the angle of the incident light.

[0165] Fig.13A and 13B Schematic diagrams of two equivalent scattering centers of dihedral angles provided by embodiments of the present disclosure are shown.

[0166] like Fig.13A and 13B As shown, the incident direction is , the reflection direction is , n is the normal of plane a, is the angle between the incident ray and plane a, It is the angle between the projection of the incident light on plane a and the vertical direction. Take a point M on the incident light, make a straight line MH through point M perpendicular to plane a, make a straight line GJ through point G perpendicular to AB, point G is the intersection of the incident light and plane a, L is the intersection of the reflected light and plane b, make a straight line LI through point L perpendicular to AB. When it is greater than 45°, make LN through point L perpendicular to the incident light. (like Fig.13A ), when the angle When it is less than 45°, make GP through point G perpendicular to the reflected light. (like Fig. 13B ).

[0167] Assume that the equivalent scattering center is at the extension line of the incident light, point K. Since the dihedral angle is 90°, it is easy to prove that LI is perpendicular to IG, so the projection of GL on plane a is GI. Since n is the normal of plane a, we can get the incident light , n and Coplanar, so the three points IGH are collinear, and the length of GK can be obtained as:

[0168]

[0169] Fig.14 A schematic diagram of the second positional relationship between the dihedral angle and the incident direction provided by an embodiment of the present disclosure is schematically shown.

[0170] like Fig.14 As shown, when the angle between the incident light and the bisector of the dihedral angle is When the light hits the back of plate b, the scattering matrix of the dihedral angle It can be expressed as:

[0171] ;

[0172] in, It is a tablet The scattering matrix, is the scattering matrix generated by the light hitting the back of plane b. and b are scattered by the plate and b the center position of the illuminated area as the scattering matrix and Scattering center. Due to the occlusion of plate b, plate Only part of the area is illuminated by light, so the plane The length of the irradiated area is:

[0173] ;

[0174] in, Is a plane Length, Is a plane Length.

[0175] Fig.15 A schematic diagram of the third positional relationship between the dihedral angle and the incident direction provided by an embodiment of the present disclosure is schematically shown.

[0176] like Fig.15 As shown, when the angle between the incident light and the bisector of the dihedral angle is When only the tablet The back side of the light is illuminated, and the scattering matrix of the dihedral angle can be expressed as :

[0177] .

[0178] Fig.16 A schematic diagram of the fourth positional relationship between the dihedral angle and the incident direction provided by an embodiment of the present disclosure is schematically shown.

[0179] like Fig.16 As shown, when the angle between the incident light and the bisector of the dihedral angle is When the incident light hits the plate and The back side of the dihedral angle.

[0180] It can be expressed as:

[0181] ;

[0182] in, and It is a metal plate and The scattering matrix.

[0183] Fig.17 The fifth positional relationship diagram of the dihedral angle and the incident direction provided by the embodiment of the present disclosure is schematically shown.

[0184] like Fig.17 As shown, when the angle between the incident light and the bisector of the dihedral angle is When only the tablet The back side of the light is illuminated by the incident light, and the scattering matrix of the dihedral angle It can be expressed as:

[0185] .

[0186] Fig.18 A schematic diagram of the sixth positional relationship between the dihedral angle and the incident direction provided by an embodiment of the present disclosure is schematically shown.

[0187] like Fig.18 As shown, when the angle between the incident light and the bisector of the dihedral angle is When the incident light hits the plate The back side of the dihedral angle. It can be expressed as:

[0188] ;

[0189] in, It is a tablet The scattering matrix, Is a plane The scattering matrix of the backside illumination. The occlusion, flat panel If only part of the area is illuminated, the plate The length of the irradiated area is

[0190] ;

[0191] in, Is a plane Length, Is a plane Length.

[0192] Fig.19A and 19B The simulated SAR image of an electric tower and the measured SAR image of an electric tower provided by the embodiments of the present disclosure are schematically shown respectively.

[0193] like Fig.19A and 19B As shown, Fig.19AThis is a simulated SAR image of a high-voltage tower target with a resolution of 0.1m, using the method proposed in this paper. Fig.19B The SAR image of the measured 0.1m resolution electric tower target is shown in Figure 2. Overall, the two images have a high visual similarity. Both the simulated image and the measured image have strong scattering intensity at some edge positions, which show obvious dihedral scattering characteristics. After refraction, the incident light can directly return to the radar receiving direction.

[0194] Fig. 20 The SAR data simulation results of the forest-power tower mixed scene provided by the embodiment of the present disclosure are schematically shown.

[0195] like Fig. 20 As shown in Table 2, the complex forest scene SAR data simulation method provided by the embodiment of the present disclosure simulates the Ku-band forest-power tower mixed scene simulation SAR image, the simulation parameters are 500m×500m, the ground height difference is 200m, the radar height is 10000 meters, the flight speed is 500m / s, and 5 high-voltage power towers are simulated in the scene, with a tower height of 25 meters. The simulation parameters are shown in Table 2.

[0196] Table 2 Simulation parameters of forest-power tower hybrid scenario

[0197]

[0198] like Fig. 20 As shown, it can be seen that the outlines of trees and high-voltage towers have certain similarities, both of which are tall structures, but the scattering of tower targets is stronger.

[0199] Fig.21 The structural block diagram of a complex forest scene SAR data simulation device provided by an embodiment of the present disclosure is schematically shown.

[0200] like Fig.21 As shown, a complex forest scene SAR data simulation device 210 provided in an embodiment of the present disclosure includes: a scene modeling module 211, a radar simulation module 212, a grid division module 213, a scattering matrix calculation module 214, and an image simulation module 215.

[0201] The scene modeling module 211 is used to construct a surface geometry model, a tree geometry model and an electric tower geometry model. The tree geometry model and the electric tower geometry model are randomly distributed on the surface constructed by the surface geometry model to generate a three-dimensional geometric model of a complex forest scene. Constructing the electric tower geometry model includes: decomposing the electric tower into a flat plate and a dihedral for model construction.

[0202] The radar simulation module 212 is used to simulate the radar emitting electromagnetic waves in the complex forest scene.

[0203] The grid division module 213 is used to grid the three-dimensional geometric model of the complex forest scene, and obtain the transmission matrix and the occlusion matrix of each grid based on the occlusion and attenuation of the electromagnetic waves in each grid.

[0204] The scattering matrix calculation module 214 is used to identify the unobstructed parts of trees, ground and power towers in each grid based on the occlusion matrix, and calculate the tree scattering matrix, ground scattering matrix and power tower scattering matrix of the unobstructed parts of trees, ground and power towers in each grid based on the transmission matrix.

[0205] The image simulation module 215 is used to perform echo simulation based on the tree scattering matrix, the ground scattering matrix and the power tower scattering matrix to obtain a three-dimensional simulated image of the complex forest scene.

[0206] In one embodiment of the present disclosure, the complex forest scene SAR data simulation device 210 provided in the embodiment of the present disclosure can be implemented as follows: Figures 1 to 20 The complex forest scene SAR data simulation method.

[0207] It is understandable that the scene modeling module 211, the radar simulation module 212, the grid division module 213, the scattering matrix calculation module 214 and the image simulation module 215 can be combined in one module, or any one of the modules can be split into multiple modules. Alternatively, at least part of the functions of one or more of these modules can be combined with at least part of the functions of other modules and implemented in one module. According to an embodiment of the present invention, at least one of the scene modeling module 211, the radar simulation module 212, the grid division module 213, the scattering matrix calculation module 214 and the image simulation module 215 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application specific integrated circuit (ASIC), or can be implemented in hardware or firmware in any other reasonable way of integrating or packaging the circuit, or in a suitable combination of software, hardware and firmware. Alternatively, at least one of the scene modeling module 211, radar simulation module 212, grid division module 213, scattering matrix calculation module 214 and image simulation module 215 can be at least partially implemented as a computer program module, and when the program is run by a computer, the function of the corresponding module can be executed.

[0208] Fig. 22 The structural block diagram of an electronic device provided by an embodiment of the present disclosure is schematically shown.

[0209] like Fig. 22As shown, the electronic device described in this embodiment includes: the electronic device 2200 includes a processor 2210 and a computer readable storage medium 2220. The electronic device 2200 can execute the above reference Figure 1 Describes the method to achieve detection of specific operations.

[0210] Specifically, the processor 2210 may include, for example, a general-purpose microprocessor, an instruction set processor and / or a related chipset and / or a dedicated microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 2210 may also include an onboard memory for cache purposes. The processor 2210 may be a processor for executing reference Figure 1 The described method flow according to the embodiment of the present disclosure may be a single processing unit or multiple processing units for different actions.

[0211] Computer readable storage medium 2220, for example, can be any medium capable of containing, storing, conveying, propagating or transmitting instructions. For example, readable storage media can include, but are not limited to, electrical, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices, devices or propagation media. Specific examples of readable storage media include: magnetic storage devices, such as magnetic tapes or hard disks (HDD); optical storage devices, such as compact disks (CD-ROMs); memory, such as random access memory (RAM) or flash memory; and / or wired / wireless communication links.

[0212] The computer readable storage medium 2220 may include a computer program 2221, which may include code / computer executable instructions, which when executed by the processor 2210 causes the processor 2210 to perform, for example, the above-mentioned combination Figure 1 The described method sequences and any variations thereof.

[0213] The computer program 2221 may be configured to have, for example, computer program codes including computer program modules. For example, in an exemplary embodiment, the codes in the computer program 2221 may include one or more program modules, for example, 2221A, module 2221B, ... It should be noted that the division method and number of modules are not fixed, and those skilled in the art may use appropriate program modules or program module combinations according to actual conditions. When these program module combinations are executed by the processor 2210, the processor 2210 may execute, for example, the above combination of Figure 1~Figure 2 The described method sequences and any variations thereof.

[0214] According to an embodiment of the present invention, at least one of the scene modeling module 211, the grid division module 212, the scattering matrix calculation module 213, and the image simulation module 214 can be implemented as a reference. Fig. 22The computer program modules described herein, when executed by the processor 2210, can implement the corresponding operations described above.

[0215] The present disclosure also provides a computer-readable medium, which may be included in the device / apparatus / system described in the above embodiments; or may exist independently without being assembled into the device / apparatus / system. The above computer-readable medium carries one or more programs, and when the above one or more programs are executed, the method according to the embodiment of the present disclosure is implemented.

[0216] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0217] Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

Claims

1. A complex forest scene SAR data simulation method, characterized in that: include: Constructing a ground surface geometric model, a tree geometric model and an electric tower geometric model, randomly distributing the tree geometric model and the electric tower geometric model on the ground surface constructed by the ground surface geometric model, and generating a three-dimensional geometric model of a complex forest scene; Simulating radar to emit electromagnetic waves in the complex forest scene; Meshing the three-dimensional geometric model of the complex forest scene, and obtaining an occlusion matrix and a transmission matrix of each grid based on the occlusion and attenuation of electromagnetic waves in each grid; Based on the occlusion matrix, determine the unoccluded parts of trees, ground and electric towers in each grid, and calculate the tree scattering matrix, ground scattering matrix and electric tower scattering matrix of the unoccluded parts of trees, ground and electric towers in each grid based on the transmission matrix, wherein calculating the electric tower scattering matrix includes: decomposing the electric tower into a plate and a dihedral angle, and respectively calculating the scattering matrices of the plate and the dihedral angle to form a tower scattering matrix together; The tree scattering matrix, the ground scattering matrix and the power tower scattering matrix are used as input simulated SAR echo data, and imaging processing is performed to obtain SAR image data of a complex forest scene; The step of calculating the tree scattering matrix, the ground scattering matrix and the tower scattering matrix of the unblocked parts of the trees, the ground and the tower in each of the grids based on the transmission matrix comprises: Based on the geometric information of the trees that are not blocked in the grid, the initial scattering matrix of the trees is calculated using the radiation transfer equation; Acquire the transmission matrix of each grid that the tree passes through in the straight-line distance from the radar, and multiply the initial scattering matrix by the transmission matrix of each grid to obtain the tree scattering matrix; The unobstructed ground surface in the grid is divided into a plurality of small planes, and an initial scattering matrix of each small plane is calculated using the OH model; Acquire the transmission matrix of each grid that each of the small planes passes through in the straight-line distance between the small planes and the radar, and multiply the initial scattering matrix of each of the small planes by the transmission matrix of each corresponding grid to obtain the scattering matrix of each of the small planes, and together constitute the surface scattering matrix; Decomposing the unobstructed electric towers in the grid into a plurality of plates and a plurality of dihedral angles, and calculating an initial scattering matrix for each plate and dihedral angle; Obtain the transmission matrix of each grid that each of the flat panels and dihedral angles passes through in the straight-line distance between the radar and the radar, and multiply the initial scattering matrix of each of the flat panels and dihedral angles by the transmission matrix of each corresponding grid to obtain the scattering matrix of each of the flat panels and dihedral angles, and together constitute the scattering matrix of the tower; The initial scattering matrix for calculating the dihedral angles consists of: Based on six positional relationships between the dihedral angle and the incident direction of the radar electromagnetic wave, an initial scattering matrix of the dihedral angle is calculated; The intersection of the two plates forming the dihedral angle is taken as the z-axis, the angle bisector is taken as the x-axis, and the y-direction is determined according to the right-hand rule. represents half of the included angle of the dihedral angle, represents the angle between the incident direction of the electromagnetic wave and the angle bisector of the dihedral angle, S1, S2, S3, S4, S5 and S6 represent the initial scattering matrices corresponding to the six position relationships, respectively. and The primary scattering matrices of the two plates represent the dihedral angles, and The primary scattering matrices of the two back surfaces of the two plates represent the dihedral angles, The secondary scattering matrix representing the dihedral angle of plane a reflected to plane b, It represents the secondary scattering matrix of plane b reflected to plane a. The side with an angle greater than 180° between the two planes is the back side. when hour, ; when hour, ; when hour, ; when hour, ; when hour, ; when hour, .

2. The method according to claim 1, characterized in that: The three-dimensional geometric model of the complex forest scene is gridded, and the occlusion matrix and the transmission matrix of each grid are obtained based on the occlusion and attenuation of the electromagnetic waves in each grid, including: Calculating the horizontal polarization attenuation coefficient and the vertical polarization attenuation coefficient of the electromagnetic wave penetrating each of the grids, setting the cross polarization to 0, and obtaining the transmission matrix of each of the grids; Calculating the surface peak point passed by the straight-line distance between the radar and the preset target position of each grid to obtain the included angle between the surface peak point and the target position in the vertical direction; When the included angle is smaller than the downward viewing angle between the radar and the target position, it is determined that the target position is not blocked by the ground surface; otherwise, it is determined that the target position is blocked by the ground surface; An occlusion matrix is ​​constructed according to whether each target position of the grid in the complex forest scene is blocked, wherein each element in the occlusion matrix corresponds to each target position in the grid, and its element value is 1 or 0, indicating that the target position is not blocked or blocked, respectively, and the target positions include the locations of trees, ground surfaces, and electric towers.

3. The method according to claim 1, characterized in that: The calculation of the primary or secondary scattering matrix for the dihedral angles includes: ； ； ； ； in, , , and represent the four diagonal elements of the primary scattering matrix or the secondary scattering matrix respectively, Indicates that the incident direction of the electromagnetic wave emitted by the radar is The angle between the projection of the plane and the x-axis, represents the incident direction of the electromagnetic wave and The plane angle, k represents the beam, r represents the distance from the radar to the target, λ represents the wavelength, a and b represent the width of the two plates of the dihedral angle that the electromagnetic wave can illuminate, and c represents the length of the two plates. and is the irradiation length of the electromagnetic wave reflected from one plane of the dihedral angle to the other plane; 4. The method according to claim 3, characterized in that When calculating the primary scattering matrix, the equivalent scattering center of the primary scattering is considered to be at the center of each plate; when calculating the secondary scattering matrix, the position of the equivalent scattering center needs to be calculated according to the angle of the incident light.

5. The method according to claim 1, characterized in that: Calculating the initial scattering matrix of the plate includes: Where S represents the scattering coefficient of the plate, represents the incident direction of the electromagnetic wave used to detect the grid, represents the polarization of the incident electromagnetic wave, Indicates the reflection direction, represents the polarization mode of the reflected electromagnetic wave, k represents the beam, a and b represent the length and width of the plate, represents the incident angle of the electromagnetic wave, represents the reflection angle of the electromagnetic wave, is the plane normal.

6. A complex forest scene SAR data simulation device, characterized in that: include: A scene modeling module is used to construct a ground surface geometric model, a tree geometric model and an electric tower geometric model, and randomly distribute the tree geometric model and the electric tower geometric model on the ground surface constructed by the ground surface geometric model to generate a three-dimensional geometric model of a complex forest scene; A radar simulation module, used for simulating the radar to transmit electromagnetic waves in the complex forest scene; A grid division module, used for gridding the three-dimensional geometric model of the complex forest scene, and obtaining a transmission matrix and an occlusion matrix of each grid based on the occlusion and attenuation of electromagnetic waves in each grid; A scattering matrix calculation module is used to identify the unobstructed parts of trees, ground and electric towers in each grid based on the occlusion matrix, and calculate the tree scattering matrix, ground scattering matrix and electric tower scattering matrix of the unobstructed parts of trees, ground and electric towers in each grid based on the transmission matrix, wherein calculating the electric tower scattering matrix includes: decomposing the electric tower into a plate and a dihedral angle, and respectively calculating the scattering matrices of the plate and the dihedral angle to form a tower scattering matrix together; An image simulation module, used to use the tree scattering matrix, the ground scattering matrix and the power tower scattering matrix as input simulated SAR echo data, and perform imaging processing to obtain SAR image data of a complex forest scene; The step of calculating the tree scattering matrix, the ground scattering matrix and the tower scattering matrix of the unblocked parts of the trees, the ground and the tower in each of the grids based on the transmission matrix comprises: Based on the geometric information of the trees that are not blocked in the grid, the initial scattering matrix of the trees is calculated using the radiation transfer equation; Acquire the transmission matrix of each grid that the tree passes through in the straight-line distance from the radar, and multiply the initial scattering matrix by the transmission matrix of each grid to obtain the tree scattering matrix; The unobstructed ground surface in the grid is divided into a plurality of small planes, and an initial scattering matrix of each small plane is calculated using the OH model; Acquire the transmission matrix of each grid that each of the small planes passes through in the straight-line distance between the small planes and the radar, and multiply the initial scattering matrix of each of the small planes by the transmission matrix of each corresponding grid to obtain the scattering matrix of each of the small planes, and together constitute the surface scattering matrix; Decomposing the unobstructed electric towers in the grid into a plurality of plates and a plurality of dihedral angles, and calculating an initial scattering matrix for each plate and dihedral angle; Obtain the transmission matrix of each grid that each of the flat panels and dihedral angles passes through in the straight-line distance between the radar and the radar, and multiply the initial scattering matrix of each of the flat panels and dihedral angles by the transmission matrix of each corresponding grid to obtain the scattering matrix of each of the flat panels and dihedral angles, and together constitute the scattering matrix of the tower; The initial scattering matrix for calculating the dihedral angles consists of: Based on six positional relationships between the dihedral angle and the incident direction of the radar electromagnetic wave, an initial scattering matrix of the dihedral angle is calculated; The intersection of the two plates forming the dihedral angle is taken as the z-axis, the angle bisector is taken as the x-axis, and the y-direction is determined according to the right-hand rule. represents half of the included angle of the dihedral angle, represents the angle between the incident direction of the electromagnetic wave and the angle bisector of the dihedral angle, S1, S2, S3, S4, S5 and S6 represent the initial scattering matrices corresponding to the six position relationships, respectively. and The primary scattering matrices of the two plates represent the dihedral angles, and The primary scattering matrices of the two back surfaces of the two plates represent the dihedral angles, The secondary scattering matrix representing the dihedral angle of plane a reflected to plane b, It represents the secondary scattering matrix of plane b reflected to plane a. The side with an angle greater than 180° between the two planes is the back side. when hour, ; when hour, ; when hour, ; when hour, ; when hour, ; when hour, .

7. An electronic device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, each step of the complex forest scene SAR data simulation method described in any one of claims 1 to 5 is implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, each step of the complex forest scene SAR data simulation method according to any one of claims 1 to 5 is implemented.

Images